(a) Technical Field
The present invention relates to a fuel cell stack clamping device. More particularly, the present invention relates to a fuel cell stack clamping device, which can automatically compensate the surface pressure in a fuel cell stack to be maintained constant using the load of the fuel cell stack and an inclination of an oblique device.
(b) Background Art
Generally, a fuel cell is a device that generates electrical energy through an electrochemical reaction between hydrogen (H2) and oxygen (O2) and includes a membrane electrode assembly (MEA). The MEA includes a fuel electrode (anode) to which hydrogen is supplied and an oxygen electrode (cathode) to which air is supplied, formed on both sides of an electrolyte membrane where hydrogen ions (H+) are transmitted.
A fuel cell stack has a structure in which the MEAs and separators are sequentially stacked, and an end plate, i.e., a bipolar plate, having hydrogen inlet and outlet and air inlet and outlet is disposed on the outermost of the fuel cell stack.
In the fuel cell as described above, an output voltage of the fuel cell stack is the sum of output voltages of unit cells. Since the unit cells divided by the separators are sequentially stacked to form the fuel cell stack, the added output voltages of the respective unit cells are defined as the output voltage of the fuel cell stack.
At the same time, the performance of the fuel cell stack is evaluated by the magnitude of the output voltage, which is affected by a pressure between the separators.
In the fuel cell stack having the above configuration and operation, it is necessary to integrally connect and fix the plurality of stacked cells to prevent leakage of the fuel and form a structure as the fuel cell. Accordingly, there has been employed a method in which the unit cells are clamped with a predetermined pressure through the end plates and an elastic body such as a spring is added to the inside of the fuel cell stack in order to maintain the surface pressure in the fuel cell stack constant even in case of a long term usage.
FIG. 1 shows a conventional clamping structure for maintaining the surface pressure in a fuel cell stack, in which a plate spring 1 and a liquid chamber 2, i.e., an elastic body, are used to provide a uniform surface pressure even in a case where the load of the fuel cell stack is changed.
However, the conventional structure has drawbacks in that a lot of plate springs and liquid chambers are required according to an increase in clamping load inside the separators, thus increasing the manufacturing cost. Moreover, with the plate springs and the liquid chambers included in the fuel cell stack, the inside structure of the fuel cell stack is complicated.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.